Darcey Bussell causes something of a stir as she strolls across the 14th‑century courtyard of Dartington Hall, Devon. A striking figure in a fitted red dress, she seems charmingly oblivious to the effect she has on hundreds of queuing fans as she disappears to take the stage at the Telegraph Way With Words literary festival.

“I worked very hard to be a diva,” she sighs wryly, later that evening. “But it never worked.” To listen to Bussell – one of the best ballerinas Britain has ever produced – one would barely recognise her as an international star. By her own modest account, her early years of training were a “disaster”, her career “so fortunate”, and her svelte figure now “horribly” deteriorated. She struggled with her position at the top of ballet’s hierarchy, she says, and today still finds it difficult to “open her mouth” after years of communicating to the outside world through her body.

Yet Bussell’s CV hardly needs explaining: 20 years at the top of her profession; a starring role in the Olympics; and an acclaimed role as a judge on Saturday night favourite Strictly Come Dancing.

Her beginnings, she discloses, were less promising. Her mother had been “very against” allowing her to attend the Royal Ballet school, aged 10. “I struggled,” she says, sitting on a small stage of Dartington’s medieval Great Hall in interview with the Telegraph’s arts editor-in-chief,Sarah Crompton. “My first year was a disaster. I had a teacher who said, 'This isn’t for you, you don’t have the mentality for it, and you’re obviously not strong enough.’ But because I’d had to persuade my mother, I couldn’t back down.”

She went on to dance all the major classical roles with the Royal Ballet at the Royal Opera House, as well as guesting with the New York City Ballet, the Kirov Ballet, Hamburg Ballet and the Australian Ballet, before retiring in 2007.

“I was 38, but I had started very young,” she says. “There are always younger and better dancers fighting to get your place. You get worn down by the fight to try to stay at the top.”

Bussell, who moved to Australia with her husband and two children shortly after retirement, says she just felt “low” at first.

“I hadn’t done anything else – that was it,” she said. “And then you stop. I did just go 'help’ and think 'who am I?’ I felt incredibly lost. Luckily I was a mother, so I could latch on to that.”

Since then, she has taken over the role of judge on the BBC’s Strictly Come Dancing, joining veterans Len Goodman, Craig Revel Horwood and Bruno Tonioli, whom she call “the boys”. Bussell tells her fans that she struggled to make herself heard after joining the show in 2012.

“I shrivel into this little thing, saying 'Hello, can you hear me?’ ” she laughs. “I had spoken with my body all my life. I never had to open my mouth to make a point. When I coach dancers I always like to get on the dance floor with them or describe something by showing them. It’s very hard to not be able to move. But the boys were very supportive. And now they’re always outside my dressing room saying 'Darce, is there anything you want?’ ”

The detail meets with an approving nod from her audience, who have turned out on a balmy evening to get her book, Darcey Bussell: A Life in Pictures, signed.

How, one fan asks, does she keep her figure nowadays? “I have actually let it go horribly,” she sighs. “But I’m conscious that I don’t want to grow out of my clothes, so the thing I try to hold on to is my waist.

“If I find the pounds are going on I stop eating bread and pasta for a few weeks.” And, she adds, “only one glass of red a week”.